Vietnam's stocks fell on Thursday, dragging the benchmark index down the most since September, after the government raised prices of petroleum products on Wednesday, heightening concern inflation may quicken.

The VN Index closed 2.8 percent lower at 431.66 on the Ho Chi Minh City Stock Exchange, the biggest slump among Asia's stock benchmarks. The gauge has fallen 5.6 percent the past three days, the longest losing streak in two months. The cost of 92-RON gasoline, the most commonly used fuel grade in Vietnam, was increased to VND22,900 ($1.1) a liter from VND20,800, the Ministry of Finance said in an e-mailed statement Wednesday.

"Sentiment may be pessimistic due to the increase in the petroleum price," Cao Tan Phat, a Ho Chi Minh City-based analyst at ACB Securities Co., wrote in a note today. A "correction" in stocks gives investors an opportunity to buy, the analyst wrote.

The VN Index has surged 23 percent this year on signs consumer-price gains are slowing. The gauge slid 27 percent last year, the most among major Asian indexes, as higher interest rates to combat rising prices hurt economic growth. Inflation slowed for a sixth month in February to 16.44 percent after peaking at 23.02 percent in August.